Process of oxidation of ethyl naphthalene



May 6, 1952 R. JOHNSON 2,595,265

PROCESS OF OXIDATION OF ETHYL NAPHTHALENE Original Filed July 15, 1945Mn NAPHENATF.

ETHYL NAPHTHAL E OX I QAT LON CONVE RSION CAUSTIC EXTRACTOQ RESID 20 UE.

' 28 HYDROGENATION Fwrnsmu HYDROGEN 54 DEHYDRATION 2 CONVERSION 5?HEATER 41 CONVERTER INVENTOR. P00521- Jomvso/v.

bis r9 7'7'ORNE X Patented May 6, 1952 PROCESS OF OXIDATION OF ETHYLNAPHTHALENE Robert Johnson, Verona, Pa., assignor to Koppers Company,In'c., Pittsburgh, Pa., a corporation of Delaware Original applicationJuly 13, 1945, Serial No. 604,806. Divided and this application October5,1946, Serial 'No. 701,408. In Canada July 8,

6 Claims.

This invention relates to the manufacture of derivatives of ethylnaphthalene and more particularly is directed to processes for oxidizingethyl naphthalene.

This application is a division of my copending application, Serial No.604,806, filed July -'13, 1945, now U. S. Patent 2,468,759 issued May 3,1949.

This invention has for its 'objects to provide new and improved methodsof making derivatives of ethyl naphthalene, to provide new and improvedmethods of oxidizing ethyl naphthalene, to avoid the disadvantages ofthe prior art and to obtain advantages as will appear hereinafter. Theseobjects will become apparent as the descriptionproceeds.

The foregoing objects are accomplished in the present invention byacting upon ethyl naphthalene with oxygen in the presence of anoxidation catalyst at a reactive temperature below that at whichsubstantial dehydration of methyl naphthyl carbinol occurs. Under theseconditions the ethyl naphthalene is oxidized to a mixture of methylnaphthyl carbinol and methyl naphthyl ketone. This mixture may beutilized as such or further treated to recover the separate elements orto convert them to other desirable derivatives.

It is possible to obtain vinyl naphthalene by dehydrogenating ethylnaphthalene. As simple as this process appears, however, it iscomplicated by the difficulty of recovering the vinyl naphthalene fromthe reaction mixture. The vinyl naphthalene so readily polymerizes thatit is difficult to separate vinyl naphthalene from the unchanged ethylnaphthalene by distillation. It is an object of the invention thereforeto provide methods for converting ethyl naphthalene to vinyl naphthalenewhich are free of these disadvantages.

This particular object is accomplished in the present invention byoxidizing ethyl naphthalene to a mixture of methyl naphthyl carbinol andmethyl naphthyl ketone, hydrogenating the methyl naphthyl ketone tomethyl naphthyl carbinol and dehydrating the methyl naphthyl carbinol tovinyl naphthalene. The unreacted ethyl naphthalene may be distilled offeither before or after hydrogenation, :or both before and afterhydrogenation, so that it is possible by the combination of steps setforth easily and effectively'to obtain a high yield of vinyl naphthaleneuncontaminated with ethyl naphthalene.

In carrying out the methods of the invention the ethyl naphthalene isfirst oxidized to a mixture 'of methyl naphthyl carbinol and methylnaphthyl ketone by acting upon it with air or other suitableoxygen-containing gas in the presenceof an oxidation catalyst. Thetemperature during. the oxidation is carefully regulated so that it doesnot exceed that temperature at which substantial dehydration of methylnaphthyl carbinol would take place. The temperature may siutably rangeup to about 175 C. but above this temperature dehydration of methylnaphthyl carbinol proceeds too rapidly. Any lower reactive temperaturemay be used which ordinarily will not be less than about C. The pressureis not critical but may vary from atmospheric or less to 400 p. s. i. ormore. The pressure ordinarily will be moderate (less than 100 p. s. i.)in view of the high boiling point, of ethyl naphthalene.

'Manganous naphthenate has been found to be unusually'efiec'tive inpromoting the oxidation of ethyl naphthalene. With this catalyst,conversions in the order of 20-30% are obtainable at 100-125 C. Watermay be present without affecting the conversion other than to slow downthe reaction rate. "Temperatures higher than C., while permissible, werenot observed to give increased overall conversion.

Other materials observed to promote oxidation include cobalt stearate,cobalt naphthenate, cupric acetate, manganous acetate, manganouscarbonate, chromic naphthenate and a mixture of manganous acetate andbenzaldehyde.

The crude product of the oxidation consists predominantly of unreactedethyl naphthalene and the balance consists mainly of a substantiallyequal mixture of methyl naphthyl carbinol and methyl naphthyl ketonealong with small amounts of unidentified acidic and neutral byproducts.It may be treated in various ways to recover the oxygenated ethylnaphthalene.

A suitable method of refining the crude oxidation product is bydistillation. If desired, the crudepi'oduct may first be extracted withcaustic solution 'to remove the acidic constituents. The unconvertedethyl naphthalene is suificiently low boiling that it may be easilyseparated from the oxygenated compounds. The distillation should beeffected under a pressure sufficiently below atmospheric to keep thetemperature below that at which substantial dehydration of methylnaphthyl carbinol would take place. At a suitable pressure, say 3-5 min.Hg, the unconv'e'rtd ethyl naphthalene may be taken off as a first cut(120 to C. at 10 mm. Hg) and recycled to the oxidation, the mixture ofmethyl naphthyl carbinol and methyl naphthyl ketone 3 taken off as asecond out (145 to 165 C. at 10 mm. Hg) and the neutral by-products asbottoms or alternatively the mixture of methyl naphthyl carbinol andmethyl naphthyl ketone may be taken ed in the bottoms along with theneutral by-products. These mixtures of alcohols and ketones may beutilized as such or passed on for further processing. Thus the mixturemay be subjected to hydrogenation according to a preferred process ofthe invention in order to convert the ketone to an alcohol, or themixture may be otherwise treated to separate the alcohol and ketone, forexample by esterifying the alcohol and then distilling the ketone awayfrom the ester. These and other methods may be utilized for recoveringthe various products of the oxidation.

The following table illustrates a typical product distribution:

TABLE I Oxidation of ethyl naphthalene at 100 and 125 with 1.5% ofmanganese naphthenate catalyst Acidic by-products 39 37 30 1 Mixedisomersabout 50% alpha and 50% beta.

The oxidation products were extracted with caustic to remove acidicby-products. The acids were liberated from caustic with acid, taken upin ether, and weighed after solvent removal. The neutral products weredistilled at 3-5 mm. to effect separation into unreacted ethylnaphthalene, methyl naphthyl ketone methyl naphthyl carbinol, and aresidue of distillation containing the higher boiling neutral productsof oxidation. The products were distilled at low pressure in a columnwith low pressure drop (Vigreux type) to avoid dehydration of methylnaphthyl carbinol.

In the accompanying flow sheet there is illustrated diagrammaticallyapparatus suitable for carrying out the oxidation and separationdescribed above. Ethyl naphthalene and manganous naphthenate areintroduced into the receiver l and the solution of manganous naphthenatein ethyl naphthalene is passed through line 2 into a converter 3provided with a suitable jacket 4 through which a heat transfer mediummay be circulated to maintain the desired temperature in the converter.Simultaneously air is forced into the bottom of the converter bycompressor 5, bubbled up through the ethyl naphthalene solution andvented through vent 6. The oxidation product is withdrawn through line!into a caustic extractor 8 where it is washed thoroughly with sodiumhydroxide solution. This solution, containing the acidic by-products, iswithdrawn through line 9 and the washed product is passed through line10 to filter l1 where the manganous hydroxide and oxide precipitate inthe solution are filtered off. The filtrate passes through line 12 intoa distillation column 13. The first fraction is taken off as overhead,condensed in a suitable condenser M and collected in a receiver I5whence it is pumped back to the receiver 1 through line It. The secondfraction is taken off as bottoms and further fractionated in column 11.A mixture of methyl naphthyl carbinol and methyl naphthyl ketonedistills over and a residue of tarry materials is left as bottoms. Thedistillate is condensed in condenser I8 and collected in receiver IQ foruse as such or for further processing.

In accordance with a preferred operation of the invention the mixture ofmethyl naphthyl carbinol and methyl naphthyl ketone obtained in theoxidation of ethyl naphthalene, either crude or refined as describedabove, is hydrogenated to yield a product which is predominantly methylnaphthyl carbinol by acting upon the mixture with hydrogen in thepresence of a hydrogenation catalyst at a reactive temperature belowthat at which substantial dehydration of the methyl naphthyl carbinoltakes place. The temperature may suitably range up to about 175 C. butabove this temperature dehydration of methyl naphthyl carbinol proceedstoo rapidly. Any lower reactive temperature may be used which ordinarilywill not be less than about 100 C.

A copper chromite catalyst has been found suitably effective inhydrogenating methyl naphthyl ketone. With this catalyst, conversion inthe order of 94% of theory was obtained at 100 to 125 C. Otherhydrogenating catalysts, such as nickel'and nickel alloy catalysts, maybe used. Nickel catalysts are less desirable, however, since they arelikely to cause hydrogenolysis of the oxygenated product to ethylnaphthalene.

In this operation the methyl naphthyl ketone is reduced to methylnaphthyl carbinol and small amounts of by-products are either formedduring the hydrogenation or carried through from the original crude. Thehydrogenated product may therefore be treated to recover the desiredproduct methyl naphthyl carbinol in a relatively pure form. This may beeifected by distilling the crude hydration product at a pressuresufficiently below atmospheric to give a temperature below that at whichsubstantial dehydration of the methyl naphthyl carbinol takes place. Ata suitable pressure, say 4-10 mm. Hg, 2. low boiling fraction (130 C. at4 mm. Hg) may be taken ofi as the first cut and either discarded orreturned to the oxidation and the methyl naphthyl carbinol may be takenoff as the second cut (130-140" C. at 4 mm. Hg) and utilized as such orsubjected to further processing such as crystallization. The residue maybe discarded.

The following table illustrates a typical product distribution:

TABLE II Hydrogenation of methyl naphthyl ketone in the ketone-carbinolmixture to methyl naphthyl carbinol Grams of charge grams.. 639 2, 200Grams of catalyst do- 50 Temperature, C 115-120 Product Analysis:(distillation at 2-4 mm Forerunnings bp 85-130 mm. 25 100 MethylNaphthyl Carbinol bp -140/4 mm 517 1, 745

Residue. slight slight maintain the catalyst at the desired temperature.Hydrogen 'is introduced at 24, bubbled up through the converter Zlgandvented at 25. 'The hydrogenated product passes out of the converterthrough line 26 into the distillation column 21. The light ends arecondensed by a condenser 28 and collected in receiver 29 whence they arereturned through lines 30 and. Hi to receiver l.

The bottoms are passed through .line 31 .into a.

second column. 32 where methyl naphthyl carbinol is taken oil asoverhead and any residue as bottoms. The methyl naphthyl carbinolfraction is condensed in a condenser 33 and collected in a receiver 34.whence it may be withdrawn for use as such or for further processing.

Inaccordance with a preferred, embodiment of the invention the methylnaphthyl carbinol recovered from the hydrogenation operation isconverted to vinyl naphthalene by passing methyl naphthyl carbinol incontact with a dehydration catalyst which suitably is a surface catalystsuch as activated alumina. Under suitable conditions of temperature andpressure dehydration of the methyl naphthyl carbinol is effected. At atemperature of 140 C. methyl naphthyl carbinol is stable for alongperiod; at 160 C. it is 20% dehydrated in two hours and at 250 C. itis dehydrated in six hours. At higher temperatures and in the presenceof a suitable dehydration catalyst, methyl naphthyl carbinol may besubstantially completely dehydrated. Unless care is utilized, however,the vinyl naphthalene formed in the dehydration is substantiallypolymerized.

In order to avoid polymerization of vinyl naphthalene in thedehydration, it is necessary to satisfactory. It is possible also toobtain. vinyl naphthalene byd istilling-methyl naphthyl carbinol overcaustic soda in a suitable high vacuum, low pressure drop'still'.Distillation without polymerization of vinylnaphthalene, however, isdifficult and it is preferred, therefore, to eifect dehydration over asurface catalyst.

The dehydration is most suitably effected at atmospheric pressurealthough higher or lower pressures, while not economical, neverthelessmay be used. It is desirable to reduce the partial pressure .of themethyl naphthyl-carbinol vapors over the surface catalystby dilutingthem with a suitable inert diluent gas such as carbon dioxide.

A. product may be thus obtained which is sufficiently pure for technicalpurposes. Where a more highly refined product is desired however orwhere the dehydration through inactivation of catalyst leaves asubstantial proportion of the methyl naphthyl carbinol unchanged, theproduct may be purified .by distillation at a pressure sufficientlybelow atmospheric to give a temperature below that at which substantialpolymerization of vinyl naphthalene takes place. Unlike the case ofethyl naphthalene and vinyl naphthalene the boiling points of methylnaphthyl carbinol and vinyl naphthalene are sufliciently diifer'ent thatseparation may easily be efiected. By efiecting distillation at apressure suitably below atmospheric in a high vacuum, low pressure dropstill, the vinyl naphthalene may be distilled free of the methylnaphthyl carbinol without objectionable polymerization.

The following table illustrates typical product distribution:

TABLE III Dehydration of methyl naphthyl carbinol to vinyl naphthaleneover activated alumina with and without 002' as diluent Product AnalysisLiquid Total Temp so M015 of Space Gas Catalyst flgggg Yeloc- 5 mCondition t gg ity Naphtha- Naphthyl lene Oarbinol 1 Liquid'spacevelocity is equivalent to m1. of methyl naphthyl carbinol per ml. ofcatalyst per hour.

I Total gas space velocity is equivalent to ml. of gaseous methylnaphthyl carbinol CO: at standard cond1tions per m1. of catalyst perhour.

1 Fresh catalyst as indlcated in the table was charged to the unitbefore starting the run whereas in other runs the catalyst frompreceding run was used.

effect a suitable balance between the temperature of the dehydrationreaction and the time of exposure. If the temperature is too high or ifthe time is too low, undesirable polymerization of vinyl naphthalenetakes place. I have found that temperatures between about 300 and 350 C.with a surface catalyst, such as activated alumina, the space-velocitymay easily be so regulated as to obtain high conversion of methylnaphthyl carbinol to vinyl naphthalene with substantially nopolymerization. Those skilled in the art will readily be able, in viewof the illustrative data given, to select space-velocities which areoptimum to minimize polymerization. Ordinarily a liquid space-velocityof about 1 or 2 is In the accompanying flow sheet, there is illustrateddiagrammatically apparatus suitable for effecting dehydration of methylnaphthyl carbinol to vinyl naphthalene. Methyl naphthyl carbinol fromreceiver 34 is passed through a line 35 into a heater 36 where it isheated as required to vaporize it. The vapors pass through line 31 wherethey are diluted with carbon dioxide at 38 into the dehydrationconverter 39. The converter 39 is packed with activated alumina ascatalyst in the converter tubes 40 which are surrounded by the jacket llby means of which a heat transfer medium may be circulated in contactwith the tubes 40. The vapors pass through line 42 into the condenser 43and the condensate is collected in the receiver 44 for use as such orfor further processing. The carbon dioxide is vented at 45. The carbondioxide may be preheated if desired to supply all or part of the heatnecessary to vaporize the carbinol. If the distillation is conductedunder optimum conditions which have been described above, high yield ofvinyl naphthalene free of polymers and methyl naphthyl carbinol may beobtained. Should substantial quantities of these products be formed,however, they may be separated by distillation. Thus the vinylnaphthalene from receiver 44 may be passed through line 46 intodistillation column 41 from which vinyl naphthalene may be recovered asoverhead, condensed in condenser 48 and collected in receiver 49 andmethyl naphthyl carbinol may be taken off as bottoms and returnedthrough line 50 to the hydrogenation conversion.

While I have described my invention with reference to particularembodiment thereof, it will be understood that variation may be madetherein without departing from the spirit and scope of the invention.

I claim:

1. In a process for producing methyl naphthyl carbinol and methylnaphthyl ketone from ethyl naphthalene, the steps of acting upon ethylnaphthalene with an oxygen-containing gas in the presence of a heavymetal salt selected from the class consisting of cobalt stearate, cobaltnaphthenate, cupric acetate, manganous acetate, manganous carbonate,manganous naphthenate, and chromic naphthenate at a reactive temperaturebelow that at which a substantial dehydration of methyl naphthylcarbinol occurs, separating ofi insoluble materials and acidicby-products, subjecting the remainder to distillation at a pressurebelow atmospheric to distill over methyl naphthyl carbinol at atemperature below that at which substantial dehydration of methylnaphthyl carbinol occurs, and recovering in said distillation a fractionboiling substantially as the mixture of methyl naphthyl carbinol andmethyl naphthyl ketone produced by the oxidation.

2. The process of claim 1 in which the oxidation is conducted at atemperature at which methyl naphthyl ketone and methyl naphthyl carbinolare the principal oxidation products.

3. The process of claim 2 in which the oxidation is effected at atemperature of about IOU-125 C.

4. The process of claim 1 in which the heavy metal salt is manganousnaphthenate.

5. The process of claim 4 in which the oxidation is conducted at atemperature at which methyl naphthyl ketone and methyl naphthyl carbinolare the principal oxidation products.

6. The process of claim 5 in which the oxidation is effected at atemperature of about -125" C.

ROBERT JOHNSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,813,606 Binaphl et a1. July 7,1931 2,302,467 Palmer et a1. Nov. 17, 1942 2,376,674 Emerson et al May22, 1945 OTHER REFERENCES Petrov et a1. (1) Papers Karpov Chem. Inst.Bach Memorial, vol. 1927, pp. 157-68 Chem. Abst., vol. 22, col. 3285(1928).

Petrov et al. (2) Trans. Karpov Inst. Chem, 1926, No. 5, pages 81-9Chemical Abstracts, vol. 22, col. 2073 (1928).

1. IN A PROCESS FOR PRODUCING METHYL NAPHTHYL CARBINOL AND METHYLNAPHTHYL KETONE FROM ETHYL NAPHTHALENE, THE STEPS OF ACTING UPON ETHYLNAPHTHALENE WITH AN OXYGEN-CONTAINING GAS IN THE PRESENCE OF A HEAVYMETAL SALT SELECTED FROM THE CLASS CONSISTING OF COBALT STEARATE, COBALTNAPHTHENATE, CUPRIC ACETATE, MANGANOUS ACETATE, MANGANOUS CARBONATE,MANGANOUS NAPHTHENATE, AND CHROMIC NAPHTHENATE AT A REACTIVE TEMPERATUREBELOW THAT AT WHICH A SUBSTANTIAL DEHYDRATION OF METHYL NAPHTHYLCARBINOL OCFURS, SEPARATING OFF INSOLUBLE MATERIALS AND ACIDICBY-PRODUCTS, SUBJECTING THE REMAINDER TO DISTILLATION AT A PRESSUREBELOW ATMOSPHERIC TO DISTILL OVER METHYL NAPHTHYL CARBINOL AT ATEMPERATURE BELOW THAT AT WHICH SUBSTANTIAL DEHYDRATION OF METHYLNAPHTHYL CARBINOL OCCURS, AND RECOVERING IN SAID DISTILLATION A FRACTIONBOILING SUBSTANTIALLY AS THE MIXTURE OF METHYL NAPHTHYL CARBINOL ANDMETHYL NAPHTHYL KETONE PRODUCED BY THE OXIDATION